中国物理B ›› 2025, Vol. 34 ›› Issue (12): 126701-126701.doi: 10.1088/1674-1056/ade8e7

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Terahertz time-domain spectroscopy to probe laser-excited spin currents in a Co/Gd system

Fan Zhang(张帆)1, Bin Hong(洪宾)2, Michel Hehn3, Rongqing Zhao(赵戎庆)1,4, Gregory Malinowski3, Yong Xu(许涌)4,†, Stéphane Mangin3, Jon Gorchon3,‡, and Weisheng Zhao(赵巍胜)1,4   

  1. 1 Hefei Innovation Research Institute, Beihang University, Hefei 230013, China;
    2 Center of Free Electron Laser & High Magnetic Field, Institute of Physical Science and Information Technology, Anhui University, Hefei 230601, China;
    3 Université de Lorraine, CNRS, IJL, F-54000 Nancy, France;
    4 Fert Beijing Institute, School of Integrated Circuit Science and Engineering, Beihang University, Beijing 100191, China
  • 收稿日期:2025-05-02 修回日期:2025-06-14 接受日期:2025-06-27 发布日期:2025-12-09
  • 通讯作者: Yong Xu, Jon Gorchon E-mail:yongxu@buaa.edu.cn;jon.gorchon@univ-lorraine.fr
  • 基金资助:
    Project supported by the National Key Research and Development Program of China (Grant No. 2023YFF0719200), the National Natural Science Foundation of China (Grant No. 62105011), and the French National Research Agency ANR through the UFO project (Grant No. ANR-20-CE09-0013), the SLAM project (Grant No. ANR-23-CE30-0047), the MAT-PULSE-Lorraine Université d’Excellence project (Grant No. ANR-15-IDEX-04-LUE), and through the France 2030 Government Grants PEPR Electronic EMCOM (Grant No. ANR-22-PEEL-0009).

Terahertz time-domain spectroscopy to probe laser-excited spin currents in a Co/Gd system

Fan Zhang(张帆)1, Bin Hong(洪宾)2, Michel Hehn3, Rongqing Zhao(赵戎庆)1,4, Gregory Malinowski3, Yong Xu(许涌)4,†, Stéphane Mangin3, Jon Gorchon3,‡, and Weisheng Zhao(赵巍胜)1,4   

  1. 1 Hefei Innovation Research Institute, Beihang University, Hefei 230013, China;
    2 Center of Free Electron Laser & High Magnetic Field, Institute of Physical Science and Information Technology, Anhui University, Hefei 230601, China;
    3 Université de Lorraine, CNRS, IJL, F-54000 Nancy, France;
    4 Fert Beijing Institute, School of Integrated Circuit Science and Engineering, Beihang University, Beijing 100191, China
  • Received:2025-05-02 Revised:2025-06-14 Accepted:2025-06-27 Published:2025-12-09
  • Contact: Yong Xu, Jon Gorchon E-mail:yongxu@buaa.edu.cn;jon.gorchon@univ-lorraine.fr
  • Supported by:
    Project supported by the National Key Research and Development Program of China (Grant No. 2023YFF0719200), the National Natural Science Foundation of China (Grant No. 62105011), and the French National Research Agency ANR through the UFO project (Grant No. ANR-20-CE09-0013), the SLAM project (Grant No. ANR-23-CE30-0047), the MAT-PULSE-Lorraine Université d’Excellence project (Grant No. ANR-15-IDEX-04-LUE), and through the France 2030 Government Grants PEPR Electronic EMCOM (Grant No. ANR-22-PEEL-0009).

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摘要： Single shot all-optical switching of the magnetization by femtosecond laser pulses in rare-earth transition-metal ferrimagnetic materials is particularly promising for future ultrafast magnetic storage applications. Moreover, ultrafast laser-generated spin currents appear to play an important role in the switching process. Here, we try to separately detect the spin current from Gd in a Co/Gd bilayer system using terahertz time-domain spectroscopy. To this aim, we use different capping, buffer and embedded layers in order to tune the spin-to-charge and spin-current propagation and identify currents from each of the layers. We attribute the observed THz emission in all layers to the transition metal demagnetization induced spin currents, and detect no contribution from the Gd demagnetization. We attribute this absence of Gd-induced THz signal to the potentially slow demagnetization of Gd, which shift the emission spectra to lower frequencies, below our detection capabilities. These results highlight the limitations in using materials suffering from the so-called critical slowdown for the optimization of spintronic THz emitters.

关键词: Co/Gd bilayer, spin current, THz emission, demagnetization

Abstract: Single shot all-optical switching of the magnetization by femtosecond laser pulses in rare-earth transition-metal ferrimagnetic materials is particularly promising for future ultrafast magnetic storage applications. Moreover, ultrafast laser-generated spin currents appear to play an important role in the switching process. Here, we try to separately detect the spin current from Gd in a Co/Gd bilayer system using terahertz time-domain spectroscopy. To this aim, we use different capping, buffer and embedded layers in order to tune the spin-to-charge and spin-current propagation and identify currents from each of the layers. We attribute the observed THz emission in all layers to the transition metal demagnetization induced spin currents, and detect no contribution from the Gd demagnetization. We attribute this absence of Gd-induced THz signal to the potentially slow demagnetization of Gd, which shift the emission spectra to lower frequencies, below our detection capabilities. These results highlight the limitations in using materials suffering from the so-called critical slowdown for the optimization of spintronic THz emitters.

Key words: Co/Gd bilayer, spin current, THz emission, demagnetization

中图分类号:  (Spin dynamics)

  • 67.30.hj
85.75.-d (Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields) 75.78.Jp (Ultrafast magnetization dynamics and switching)